The purpose of this project is to provide consultation on statistical and epidemiological methodology in the design, interpretation, and evaluation of clinical trials of diagnosis, treatment, and prevention of cancer, and other studies requiring this kind of expertise. For some studies the Section provides full statistical support, including development of detailed study plans, assistance in the design of appropriate study forms, supervision of randomization (for trials) and collection, processing, and editing of data, performance of interim analyses during the progress of the study, preparation of progress reports, final analysis of study data, and collaboration in the preparation of scientific papers. During the past year the Section has continued to provide full statistical support for the randomized clinical trials of treatment conducted by the Lung Cancer Study Group and the Brain Tumor Cooperative Group. In the area of diagnosis, the Section is responsible for maintaining an up-to-date inventory and clinical data for a large serum bank containing information and sera for some 12,000 women including some with breast cancer, some with benign breast disease, and asymptomatic controls. These data are used to evaluate potential biological markers. Some other important activities under this project include (1) multiple regression analyses of risk factors for breast cancer, using data from three major national studies; (2) studies of selenium pharmacokinetics needed for possible prevention trials; (3) a study to estimate population consumption of foods thought to be protective or harmful to cancer risk; and (4) design of a new study of food purchasing behavior and consumer nutrition information.